The present invention is concerned with a sealing cap for cylindrical parts, especially for a bolt guide of a spot-type disk brake, comprising a resilient boot one end portion of which is adapted to be secured peripherally on a first cylindrical part and the other end portion of which is adapted to be secured peripherally on a second cylindrical part, and comprising a rigid insert member disposed within at least one of the end portions.
A sealing cap of this type is known from U.S. Pat. No. 4,199,159. That sealing cap was provided for a cylinder-and-piston assembly, with the piston at the outer periphery including an annular groove fitted into which is a first end portion of the sealing cap. Emerging from the first end portion, a folded section extends radially outwardly, with folds extending in the axial direction and passing over into a second end portion radially disposed further outwardly. Located in the second end portion is an insert member of substantially S-shaped configuration. The radially extending second end portion is seated in a correspondingly shaped circumferential groove in the cylinder of the piston-and-cylinder assembly. Securing of a sealing cap using the design of the reference involves substantial assembly effort as both the piston and the cylinder are required to be provided with correspondingly shaped and formed sealing grooves.
A second reference, German patent DE-OS No. 29 04 363 discloses a sealing cap for a piston-and-cylinder assembly provided with corresponding sealing grooves both in the piston and in the cylinder. An insert member in that cap is provided at the radially extending internal end portion to protrude with the one end of the resilient end portion. The folds in the sealing cap extend in a substantially radial direction. Securing that cap involves substantial effort because correspondingly shaped and processed grooves must be provided in the cylindrical portions. Difficulties are likely to arise with that cap during assembly in cases where a radially outwardly disposed portion of the one cylindrical member will cover the boot or seal so that, during assembly, it is not possible to visually determine whether the folds of the boot are regularly in place. In the absence of a way of determining the fold disposition, it is likely for the sealing cap to be damaged during relative movement between the cylindrical parts, i.e. in the present instance, between piston and cylinder, thereby preventing the cap from a reliable performance of its intended function.